The choice of a suitable system of epidural drug delivery has an important role in getting proper analgesia and a low incidence of breakthrough pain during labor. In order to develop preventive strategies for BP, some clinical scales to estimate its incidence rate have been described. Among risk factors for BP the investigators can include: Nulliparity, epidural catheter placement at an earlier cervical dilation, neonatal weight and technique performed (epidural versus combined spinal-epidural - CSE).